Functional Materials for Energy

Energy band diagrams of metal/ferroelectric (FE)/correlated electron oxide (CEO) FTJs for two polarization directions, in which the tunneling probability is controlled by the direction of the polarization, yielding either a hole accumulated (top) or a hole depleted (bottom) state in the CEO layer.

The tunneling electroresistance (TER) in ultrathin ferroelectric tunnel junctions (FTJs) is found to be critically dependent upon interface state phase transitions induced by the ferroelectric (FE) polarization. This discovery provides a comprehensive understanding on the origin of the high TER effect in FTJs and is a critical step towards designing high-density oxide transistors and non-volatile data storage.

FE control of electronic transport is one of the emerging technologies in oxide heterostructures. Many previous efforts in FTJs exploited solely the differences in the electrostatic potential across the FTJs induced by changes in the FE polarization direction. However, this work shows that in practice the junction current ratio between the two polarization states is largely influenced by the electrostatic modification in the correlated electron oxide electrodes. Therefore, our discovery of the enhanced TER effect by interfacial phase transitions ultimately highlights that the strong coupling between degrees of freedom across heterointerfaces could yield versatile and novel applications in oxide electronics.